<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div>这是div</div>
<input type="text" id="i1">
<input type="button" value="按钮" onclick="f()">
<script>
  function f(){
    //得到文本框和div
    let i =document.querySelector("#i1")
    let d =document.querySelector("div")
    //取出文本框的值并复制给div
    d.innerText = i.value;
  }
</script>
</body>
</html>